Plasma proteins and colloid osmotic pressure of blood of rat fetuses prenatally exposed to Mirex.

A significant effect of prenatal exposure to the pesticide Mirex is a fetal edema, which is responsible for many of the toxic effects of this agent. Pregnant rats were given 6 mg/kg mirex on d 8 1/2-15 1/2, a moderate dose that does not cause maternal mortality. The blood of 18 1/2- and 20 1/2-d rat fetuses was tested to determine a possible cause of the edema. There were no significant differences between fetal and maternal plasma or between control and treated fetal plasma with respect to sodium and potassium concentrations or total osmolality. The protein concentration of plasma of treated fetuses was lower than that of controls. This effect was proportional to the degree of edema. The concentration in 20 1/2-d controls was 25.2 mg/ml, that in mildly swollen treated fetuses 18.1 mg/ml, and that in severely swollen ones 13.5 mg/ml. Polyacrylamide gel electrophoresis showed quantitative and qualitative changes in plasma of affected fetuses. The colloid osmotic pressure was also reduced fron 8.0 mm in controls and unaffected treated fetuses to 4.8 mm in swollen fetuses. Since lowered plasma protein and colloid osmotic pressure cause tissue edema in adults, they are the probably cause of mirex-induced fetal edema.